Sliptreaming New Updates to an already Updated ISO?

I'm wondering what the general opinion is updating an already slipstreamed Win7 ISO?

So for example I took an OEM Win7 ISO and slipstreamed updates using RT7Lite. Then months more go by and it's time to add new updates. Should I always start with a FRESH copy of my Win7 ISO or can I reuse the one that I have already previously slipstreamed updates to? This way I would only have to add new updates rather than starting from scratch every time.

I just know that sometimes MS removes past updates and replaces them with newer updates that supersede the older ones. So I'm just not sure how that affects my Slipstreamed ISO if those past updates are already slipstreamed into it.